[A-AS12] [EE] High performance computing for next generation weather, climate, and environmental sciences using K

[AAS12-02] Tornadogenesis as revealed by high-resolution ensemble forecasts for the Tsukuba city supercell tornado on 6 May 2012

★Invited papers

*Sho Yokota¹, Hiromu Seko^1,2, Masaru Kunii¹, Hiroshi Yamauchi^3,1, Hiroshi Niino⁴ (1.Meteorological Research Institute, Japan Meteorological Agency, 2.Japan Agency for Marine-Earth Science and Technology, 3.Observations Department, Japan Meteorological Agency, 4.Atmosphere and Ocean Research Institute, The University of Tokyo)

Keywords:Tornado, Ensemble forecast, Data assimilation, Circulation analysis, K-computer

To clarify the environmental conditions for tornadogeneses, we performed ensemble-based analyses using 33-member high-resolution ensemble forecasts of the Tsukuba city supercell tornado on 6 May 2012. The horizontal resolution of the model was 50 m. The initial and boundary conditions were taken from ensemble forecasts with 350-m horizontal resolution started from local ensemble transform Kalman filter analyses with 1875-m horizontal resolution, which assimilated four C-band radars and dense surface data. The results of backward trajectory analyses of parcels that were placed in forecasted near-surface tornado-like vortices showed that the circulation of the vortices can be generated due to both surface friction and baroclinity, but the way the circulation is generated did not appear to be essential for determining whether tornadoes are generated or not. On the other hand, the mesoscale environment such as the strength of low-level mesocyclones at about 1-km height and near-surface humidity had strong correlations with the maximum vertical vorticity of the tornado-like vortices, indicating that these factors seem to be essential for a tornadogenesis.

Acknowledgement:
This work was supported in part by the research project “HPCI Strategic Program for Innovative Research (SPIRE) Field 3,” “Social and Scientific Priority Issues (Theme 4) to Be Tackled by Using Post K Computer of the FLAGSHIP2020 Project,” “Tokyo Metropolitan Area Convection Study for Extreme Weather Resilient Cities (TOMACS),” JSPS KAKENHI Grant Numbers JP24244074 and JP16K17804, and the Cooperative Program (No. 131, 2014; No. 136, 2015; No. 138, 2016) of Atmosphere and Ocean Research Institute, The University of Tokyo. Experiment with 350-m and 50-m horizontal resolution were conducted using the K computer at the RIKEN Advanced Institute for Computational Science through the HPCI System Research Project (Project ID: hp120282, hp130012, hp140220, hp150214, hp150289, hp160229). Observational data were provided from Japan Meteorological Agency and NTT DOCOMO, Inc.